Microalbuminuria in hypertension: Measurement, variations, interpretation and recommendations

Permanent hypertension is frequently associated with increased glomerular p ermeability to albumin at an early stage, indicating renal involvement and endothelial dysfunction. The definition of microalbuminuria is an urinary a lbumin excretion of 30-300 mg/24 hrs, confirmed on two occasions over a 3 m onth period. It may also be expressed in mug/min, m/l or mg/mmol of creatin ine, Radio-immunological, immunonephelometric methods and Elisa are specifi c and the most sensitive methods of measurement. There is a large intra-ind ividual variability (23-60%) making it essential to repeat measurements alw ays by the same technique. The prevalence of microalbuminuria is 5-8% in the general population and 6- 24% in hypertensive patients. When present, it is a marker of increased car diovascular risk. Clinical recommendations suggest adaptation of urinary co llection according to the context : screening. diagnosis or clinical resear ch. It is always necessary to start by dip-stick detection of proteinuria, haematuria or urinary infection. Clinical research requires repeated measur ement of 24 hour microalbuminuria, sometimes divided into two periods of da y and night, often associated with ambulatory blood pressure recordings and renal function tests. Studies of the effects of anti-hypertensive drugs on microalbuminuria could provide better evaluation. In conclusion, measurement of microalbuminuria remains a tool of clinical r esearch allowing an assessment of cardiovascular and renal risk of hyperten sive patients.